The invention relates to a preparation method of a nanometer thin-layer structural carbon material. The preparation method comprises the following steps of: effectively controlling the formation, growth and fusion of an intermediate in a carbonizing process by taking pitch as a raw material and adopting a mechanical method cooperated with coal pitch modification to obtain a carbon material intermediate with an optical microscopic structure showing a good fiber structure; then calcining to obtain the nanometer thin-layer structural carbon material with the microscopic structure which is very clear in structure. The preparation method disclosed by the invention has the greatest advantages of preparing a macroscopic quantity of nanometer thin-layer materials, being low in raw material price and simple in process flow, being hopeful to carry out large-scale production in industrial production and overcoming the defect that the preparation of the similar material reported at present can only obtain a milligram-grade quantity which only achieves the quantity level needed by laboratory research.